Geology 141(B): Fall, 2008Lecture Final Examination... Page 1 ...
Geology 141(B)Name .
Fall, 20083:30 p.m.13 December, 2008
GE141(B):
Earth and Environment
Final Examination
INSTRUCTIONS: PLEASE read these instructions and questions CAREFULLY and completely. If you do not understand a question as it appears on the exam, PLEASE ASK FOR CLARIFICATION!! It is to YOUR benefit to do so. This examination is worth 300 points, or 30% of your overall semester grade. Exams will be graded as quickly as possible; your individual point total will be entered on the last page to ensure that only you know how well you did on the exam, unless you choose to divulge that information to others.
Please remember that I CANNOT give any credit for responses I can't read! The number of points for each question is indicated in parentheses after the question.
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"One of the illusions of life is that the present hour is not the critical, decisive hour. Write it on your heart that every day is the best day of the year."
- Ralph Waldo Emerson
Section I: Multiple choice. Please circle the letter of the response that is correct or that BEST answers the question or completes the statement. Please read each question and possible response carefully. There is ONLY ONE BEST ANSWER for each question. Each question is worth 5 points; this section is therefore worth 200 out of the total of 300 for the exam. PLEASE READ EACH QUESTION AND RESPONSE OPTION CAREFULLY! I am not trying to trick you, but missing a key word in a question can result in an error in judgment!
1. The most abundant two elements in the Earth's crust, by weight, are
a. iron and siliconc. iron and magnesium
b. oxygen and silicond. iron and nickel
2. Minerals are classified into different major groups based on
a. their chemical composition.
b. where they occur within the Earth - crust, mantle, core, etc.
c. whether they are natural or man-made.
d. their crustal structures.
3. Rocks are classified into different major groups based on
a. their chemical composition.
b. whether they are natural or man-made.
c. where they occur within the Earth - crust, mantle, core, etc.
d. their mode of origin - how they came into existence.
4. The only non-silicate mineral group that is important principally for its abundance in the Earth's crust, rather than its economic significance, is the
a. feldsparsc. oxides and hydroxidese. sulfates
b. carbonatesd. sulfidesf. halides
5. The San Andreas Fault of California is an example of a(n)
a. transform boundary, where one tectonic plate is sliding past another.
b. subduction zone, where the Pacific Plate is being pushed beneath California.
c. spreading center, where new crust is being created, ultimately to split
California off from the rest of the U.S.
d. active rift zone, like the East African Rift valley.
6. What is an extremely common and critically important ionic substitution pair in the composition of silicate mineral structures?
a. Si and Alc. Al and Fe
b. Si and Od. Si and Fe
7. A magma that is relatively low in silica (52%), and has relatively high contents of iron, magnesium, and calcium, will when erupted from a volcano most likely yield a
a. basalt, with plagioclase, olivine and pyroxene.
b. granite, with plagioclase, orthoclase, hornblende, biotite and quartz
c. gneiss, with plagioclase, orthoclase, hornblende, biotite and quartz
d. rhyolite, with plagioclase, sanidine [volcanic counterpart to orthoclase],
biotite, and quartz.
8. While visiting friends on a tropical island paradise over JanPlan, you gaze off into
the distance and spy an island with the profile shown above. They tell you it's called "Hat Island" and is supposed to be cursed - so no one ever goes there. You, however, know that with this form, and where you're located, this is most likely a(n)
a. stratovolcano formed on a subduction zone, part of an island arc system.
b. shield volcano, formed above a mantle plume.
c. ophiolite fragment from an ancient continent-continent collision.
d. accreted terrane brought here by sea-floor spreading.
9. Clay minerals originate from
a. high-silica magmas crystallizing in shallow underground plutons.
b. chemical reactions in the deep ocean basins, around "black smokers."
c. hydrothermal alteration of silicate minerals to carbonates.
d. chemical weathering of other silicate minerals.
10. An arkosic graywacke (a muddy, feldspar-rich sandstone) begins to subduct along the Andean margin of South America. The pressures increase more rapidly than the temperatures, but with all the water present in the pores of the rock it eventually succumbs and melts. When this material recrystallizes, what rock will result?
a. eclogitec. quartzitee. blueschist
b. granited. marblef. slate
11. The source for all the heat that drives plate tectonics is
a. the sund. left over from the Big Bang
b. radioactive decaye. the Earth's magnetic field
c. volcanoes
12. The difference between metamorphic grade and metamorphic facies is that
a. metamorphic grade is a natural product, whereas metamorphic facies
refers to human-induced changes on rocks.
b. metamorphic grade is a crude approach - low, medium, high - whereas
metamorphic facies allows differentiation of the effects of heat and
temperature.
c. metamorphic facies is a natural product, whereas metamorphic grade
refers to human-induced changes on rocks.
d. metamorphic grade refers to how much the rock has changed, whereas
metamorphic facies just refers to how different it looks to the eye.
13. The Earth, and our Solar System, are believed to be about how old?
a. 5 million yearsc. 12-15 million years
b. 5 billion yearsd. 12-15 billion years
14. Radiometric dating in its many forms is a reliable tool for dating most non-sedimentary rocks because
a. most non-sedimentary rocks contain radiocarbon.
b. radiometric decay rates are invariably constant.
c. non-sedimentary rocks were created in the Big Bang.
d. most rocks contain some hydrogen and helium left over from their origin.
15. You were hiking last summer in the wilds of Montana and encountered a deep canyon wall where the following stratigraphy was displayed. At the time, you just thought the rocks were really messed up, but now you realize that this was
just an example of where the rocks had been deformed, probably long ago, by
a. compressional forces producing folding and a thrust fault.
b. tensional forces producing folding and a thrust fault.
c. compressional forces producing folding and a normal fault.
d. shearing forces producing folding and a left-lateral fault.
16. A catastrophic earthquake of magnitude 9, like Banda Aceh on December 26, 2004, represents about how much more ground movement (shaking) than a minor earthquake of magnitude 3, like that which occurred in western Maine this semester? About
a. three times as muchc. 100 times as much e. 10,000 times as much
b. 30 times as muchd. 1000 times as much f. a million times as much
17. The epicenter of an Earthquake is the
a. place where the rocks originally fail in an earthquake.
b. same thing as the magnitude of the earthquake.
c. nearest major town or city to where the earthquake occurred.
d. the location on the ground surface above the initial rock failure in the 'quake.
18. Mountain-building processes at convergent plate margins will be dominated by
a. compressional stressc. shearing stress
b. tensional stressd. no one particular kind of stress
19. Where would you expect to find thrust faults being generated (created) in the modern world?
a. in Hawai'ic. in the Himalaya
b. in Kentuckyd. on the MORRS
20. Which of the following precursor signs is not a part of the "dilatency hypothesis" for predicting that an earthquake will happen in the near future?
a. water levels drop in wells
b. pets run away or act strangely
c. electrical resistivity (resistance to the passage of an electrical current) of
rocks drops, then rises
d. radioactivity levels in well waters increases
21. Most tsunami (often erroneously called "tidal waves") are generated by
a. undersea disturbances caused by earthquakes, landslides, or volcanism.
b. the gravitational pull of the sun and moon on the Earth.
c. large ships traveling too fast through narrow areas in the ocean (straits, etc.)
d. migrating large schools of fish, that create ocean currents as well.
22. In an earthquake, seismic energy is released in a variety of waves. Which are those that do the most damage to structures and thus cause the greatest misery (and cost) in human terms?
a. P-wavesc. surface waves
b. S-wavesd. refracted P-waves
23. While flying into Southern California for a JanPlan internship, you looked down and saw a highway and orange groves offset as shown below. Because you paid close attention in your geo class, you know that you've flown over a typical example of a
a. normal faultc. reverse faulte. right-lateral fault
b. thrust fault d. drag fault f. left-lateral fault
24. Water is a key ingredient leading to mass wasting in geologic environments because it
a. lubricates intergrain contact points.
b. adds mass to the geologic materials on a slope.
c. exerts pore pressures that push uncemented grains apart.
d. is key to chemical weathering processes that weaken rocks.
e. can freeze and thaw, forcing even solid rocks apart.
f. all of the above.
25. The sketch-map below shows a section of the Whatsatooya River in Munkatawagog County, Georgia.
EROSION is going to be the dominant geologic process taking place at locations labeled
(a) A (b) B (c) C (d)D (e) E (f) C & D (g) B & E
26. On the map area above, in what areas would you be most likely to find sand and/or gravel being deposited?
(a) A (b) B (c) C (d)D (e) E (f) C & D (g) B & E
27. On the map area in Fig. 25, what feature represents a former portion of the river channel?
(a) A (b) B (c) C (d)D (e) E (f) C & D (g) B & E
28. Most sediments that wind up in streams get there as a result of
a. mass wasting of the channel banks.
b. human activities that increase erosion rates.
c. chemical weathering of rocks in the streams.
d. downcutting of the streams into underlying sedimentary deposits.
29. Materials typically comprising the suspended load of streams will be
a. dissolved organic compounds and weathering products, like bicarbonate
ions (HCO3)- .
b. sand and fine gravel.
c. silts and clays, and some solid organic matter.
d. you can't say without more information.
30. The competence of a stream is defined as
a. how much total sediment a stream can transport.
b. how much water the stream can hold without flooding.
c. how large a boat can be floated on the stream.
d. the largest clasts a stream can move in the bed load.
31. Perennial streams are maintained in prolonged times of no rain by
a. rain somewhere else in the drainage basin.
b. melting snow or ice elsewhere in the drainage basin.
c. flow of groundwater through springs in the drainage basin.
d. inflow of intermittent tributary streams in the drainage basin.
32. About 97% of the world's water is in the oceans. Almost another 2% is tied up in glacial ice. Nearly 1% (almost all that's left) of the world's available water is to be found in
a. lakes and pondsc. the atmosphere and biospheree. the mantle
b. groundwaterd. streams and rivers
33. An aquifer is a(n)
a. water-carrier, like a river or stream, either above ground or underground.
b. rock or sediment unit with high porosity, permeability, and potable water.
c. large unit of water, such as a lake or even a glacier.
d. a water-soluble rock unit, leading to karst environments.
34. Karst environments and caves are most commonly found in areas underlain by
a. limestonec. granite
b. basaltd. unconsolidated sands and gravels
35. How many times has the Earth been glaciated in its history?
a. only once, in the Great Ice Age.
b. twice, in the Great Ice Age and in the late Precambrian "Snowball Earth."
c. three or four times, including in Gondwanaland when Pangaea existed.
d. hundreds of times over its history.
36. Glacial-Interglacial fluctuations (i.e., advancing and retreating of glaciers on a regular cycle) are governed by
a. global plate tectonics.
b. Milankovich cycles of the Earth's orbital parameters.
c. the position of the stars relative to the Earth's surface.
d. gravitational pull of the sun and moon on the Earth.
37. Waves that come in from the ocean (or a lake) to strike against a coast are created by
a. frictional drag of the Sun's gravitational pull on the water surface.
b. frictional drag of winds blowing over the water surface.
c. the gravitational pull of the Sun and Moon on the water, and the Earth's
rotation beneath the resulting "bulge" in the water.
d. longshore drift of sediments along the coastline, refracting wave activity
from distant earthquakes and undersea volcanism on the MORRS.
38. Cliffed coasts, such as those of Maine, California, Oregon, Washington, British Columbia, southeastern Alaska, and elsewhere, are all maintained by
a. constant glaciation that erodes the coastlines.
b. deposition of coarse-grained sediments in steep beach faces.
c. undercutting, mass wasting, and longshore drift removing the sediments.
d. tectonic uplift of coral reefs, like atolls, along the coastline.
39. The difference between resources and reserves is that
a. resources are what a society wants, reserves are what it absolutely has to
have to survive.
b. resources are what a society needs, reserves are those resources that are
available at acceptable cost.
c. reserves are what a society needs, resources are those reserves that are
available at acceptable cost.
d. resources are needed by primitive societies, whereas reserves are those that
are needed by industrial societies.
40. Major mining districts are almost always located on modern or ancient tectonic plate boundaries because
a. this is where many of the ore-forming processes take place, since they
require heat and magmas for their formation.
b. this is where the mantle rocks are pushed up high enough that they can be
mined.
c. these are areas where the Earth's magnetic field has attracted many
meteorites, which carried the economically valuable minerals to Earth.
d. these are areas where enhanced groundwater flow has concentrated
economically valuable minerals.
Section II: Short answers, fill-ins, etc. Please respond to each question in the most appropriate fashion; make your responses concise and to the point, but thorough. There should be ample space provided for an adequate response. PLEASE WRITE LEGIBLY; I can't give credit for responses I can't read! Please make all verbal responses in complete sentences and proper English and avoid using cryptic abbreviations or shorthand notation such as b/c, w/, etc. The number of points for each question is indicated in parentheses after the question; there are 100 points possible for the entire section. (And PLEASE remember that, as promised on the syllabus, I will deduct a point each time I see "volcanoe" or "techtonic!" )
IMPORTANT! Please note that the space left behind a question should be sufficient to properly respond thoroughly. An 8-centimeter space should be taken as a major hint that you need more than two or three words to respond adequately to a given question.
41. Identify three independent lines of evidence, other than the apparent fit of continental margins, that support the combined theories of continental drift and plate tectonics. Indicate clearly HOW each of these lines of evidence provides independent support for the theories. (BE CAREFUL TO AVOID CIRCULAR REASONING!!! 10 points)
42. Hydrolysis is an extremely important chemical weathering process, by which minerals (typically silicates) formed at high temperatures and pressures, are recrystallized (though chemical reactions with water) to forms more stable at the Earth's surface temperatures and pressures. What are the four principal or common products of hydrolysis of a typical silicate mineral? (5 points: 2-1-1-1)
1.
2.
3.
4.
43. In the chart below, I've indicated the size ranges for various clastic sediments. Name the sediments that are characterized by those size clasts (I've given you the first), and identify the sedimentary rocks that are created by the cementation and compaction of those sediments (10 points - 1 point each).
Size| Sediment Name|Sedimentary Rock
||
> 256 mm|Boulders|
||
|| (rounded clasts)
2 - 256 mm||
||
||
0.06 - 2.0 mm||
||
||
0.004-0.06 mm||
||
||
|| (massive)
<0.004 mm||------
|| (fissile)
||
44. What is flocculation, and why is it important? (5 points)
45. While waiting in line at the supermarket, you spy a headline in the WEEKLY WORLD NEWS that reads, "RADIOCARBON DATING OF LAVAS PROVES HUMANS LIVED ALONGSIDE DINOSAURS 1 MILLION B.C.!" Other than the fact that you know humans and dinosaurs did NOT coexist at any time in the Earth's history, what are two technical reasons why you will immediately recognize this as a specious story intended to mis-lead the uneducated to believing there's scientific evidence for this fantasy? (10 points)
1.
2.
46. What are three major factors that will determine whether a portion of the Earth's crust will fold or break (fault) in response to compressional stress at a subduction zone? (5 points: 2-2-1)
1.
2.
3.
47. A stream channel is 15 feet wide and averages 3 feet deep. The average velocity of water flowing in the channel is 2 feet per second. The suspended sediment load is approximately 10 grams per gallon. There are approximately 8 gallons (U.S.) per cubic foot of water, and about 35 feet in one cubic meter. What is the discharge of this stream, including the proper units? (5 points)
48. Why do all the mountain ranges from Utah west across Nevada and into eastern California, ending with the Sierra Nevada, run north-south? What kind of process(es) and forces have produced these mountains, and give the region the name of the Basin and Range of the United States? (10 points)